BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] The present invention relates to a magnetic recording/playback apparatus and, more
particularly, to a mechanism for imparting tension to a magnetic tape in such an apparatus.
DESCRIPTION OF THE RELATED ART
[0002] An arrangement in which power is transmitted from a pulley provided on a direct drive
capstan motor (DD capstan motor) to a rewinding mechanism through a belt is generally
known as a take-up-reel driving mechanism in a magnetic recording/playback apparatus
such as a video tape recorder (VTR).
[0003] In such a magnetic recording/playback apparatus, in a pause during recording or playback,
namely, a mode called "pause", "still" or "slow", when the running of the capstan
motor is stopped, it is necessary to apply a certain brake load to the motor. The
reason for this is that a so-called backlash-the phenomenon in which the capstan motor
itself is reversed due to tension created by extension or contraction of the aforesaid
power transmission belt. When this backlash phenomenon occurs, tension which acts
on the recording tape lowers, thus resulting in the deterioration in apparatus performance
which may lead to, for example, the occurrence of noise on a screen. One method of
applying a brake load is to press a brake pad or the like against the outer periphery
of the rotor (or object integral therewith) of the capstan motor. A method employing
a solenoid is disclosed in, for example, Japanese Patent Unexamined Publication (called
Tokkyo Kohkai) No. 60-171657. In the VTR disclosed in Tokkyo Kohkai 60-171657, a solenoid
(75) is utilized to bring a brake pad (77) into and out of contact with the lower
face of a fly wheel (74) which is secured to the capstan shaft (72) of a capstan motor
(73).
[0004] In such a conventional example of the type in which the brake pad is pressed against
the outer periphery of the rotor (or object integral therewith) of the capstan motor,
a transition period is required to cause the mechanism to proceed to a brake mode
and, in addition, an exclusive space for the brake mechanism needs to be assured.
As a result, there are a number of problems: for example, (1) insufficient operational
response; (2) an increase in the complexity of the structure of the apparatus; and
(3) deviation from the general trend toward miniaturization of the apparatus. The
above-described arrangement in which the brake pad is moved by the solenoid also involves
a number of problems: for example; (1) large electric power is required to activate
the solenoid; (2) the reliability of the operation is insufficient; (3) an increase
in the weight of the apparatus is incurred; and (4) costs are increased due to the
expensive price of the solenoid.
SUMMARY OF THE INVENTION
[0005] It is a primary object of the present invention to solve the above-described problems
involved in the prior art.
[0006] This object is achieved by providing an improvement in a magnetic recording/playback
apparatus of the type which utilizes a take-up reel driving mechanism arranged to
transmit power from a pulley to a take-up reel driving mechanism through a belt, the
pulley being provided on a direct drive capstan motor, and which is arranged to draw
a recording tape into a predetermined path for purposes of recording or playback.
The improved magnetic recording/playback apparatus is provided with a rotary head
cylinder arranged to record signals on the recording tape and to play back signals
recorded on the recording tape; a pinch roller cooperative with a capstan shaft to
clamp and drive the recording tape; and a tension imparting member capable of coming
into and out of contact with the recording tape and arranged to press the recording
tape by a predetermined pressure by means of the urging force of an urging spring
during one of recording, playback and a pause.
[0007] The tape tension imparting member operates in accordance with a decrease in tape
tension which occurs when the recording tape is reversed due to the backlash of the
capstan motor which is caused by the extension or contraction of the belt through
which power is transmitted from the direct drive capstan motor to the take-up-reel
driving mechanism. In consequence, the decrease in tape tension is prevented.
[0008] To explain in further detail, the tape tension imparting member can be urged by a
spring, e.g., a torsion spring, to come into and out of contact with the recording
tape, and serves to impart a predetermined tape tension to the recording tape in contact
relationship therewith in a pause during the process of playing back signals recorded
on the recording tape or recording signals on the recording tape. The urging force
of the spring is made sufficiently small compared to the tape tension created in a
normal recording/playback state. Accordingly, while signals are being recorded or
recorded signals are being played back, the tape tension imparting member is forced
back by the recording tape with the contact relationship maintained, and the tape
tension imparting member therefore has no effect on the state of tape running. When
the backlash of the power transmission belt occurs during a pause, the capstan shaft
is reversed to make the recording tape loose. However, the tape tension imparting
member absorbs the looseness of the recording tape by pressing the recording tape
and displacing it from the ordinary running path, thereby impart a predetermined tape
tension to the recording tape, so that any drawback due to a decrease in tape tension
is prevented.
[0009] It is preferable that the tape tension imparting member be placed in interlocked
relationship with a pinch roller driving mechanism for moving the pinch roller toward
and away from the capstan shaft so that, when the pinch roller is placed at a stand-by
position away from the capstan shaft, the tape tension imparting member is retracted
into its stand-by position at which it does not contact the recording tape. More specifically,
as a cassette is loaded into or unloaded from the apparatus or the recording tape
is fed forward or rewound, the pinch roller is consistently placed in its stand-by
position. Accordingly, if, as one recommended form of working example, the pinch roller
driving mechanism and the tape tension imparting member are arranged in interlocked
relationship and the tape tension imparting member is arranged to move to the stand-by
position in accordance with the movement of the pinch roller, it becomes unnecessary
to separately provide a driving mechanism for the tape tension imparting member.
[0010] Accordingly, in one preferred feature of the present invention, there is provided
with a magnetic recording/playback apparatus of the type which utilizes a take-up
reel driving mechanism arranged to transmit power from a pulley to a rewinding mechanism
through a belt, the pulley being provided on a direct drive capstan motor, and which
is arranged to draw a recording tape into a predetermined path for purposes of recording
or playback. This apparatus is provided with: a rotary head cylinder arranged to record
signals on the recording tape and to play back signals recorded on the recording tape;
a pinch roller cooperative with a capstan shaft to clamp and drive the recording tape;
a pivotal arm for the pinch roller arranged to reciprocally pivot in accordance with
the motion of a cam member driven by a motor; a pinch roller shaft secured to one
end of the pivotal arm for supporting the pinch roller; an operative arm for the tape
tension imparting member pivotally supported at one end by the pinch roller shaft
and provided with a slot at the other end, the shaft for the tape tension imparting
member extending through the slot, the operative arm being restricted by the shaft
for the tape tension imparting member at the other end but permitting the pivotal
motion of the pivotal arm for the pinch roller within a predetermined range in that
the shaft for the tape tension imparting member can be relatively displaced in the
slot; a tape tension imparting member pivotally supported at one end on said shaft
for said tape tension imparting member and provided with a pressure member at the
other end and a projection at or near the other end, the pressure member extending
parallel with the axis of the shaft for the tape tension imparting member and serving
to smoothly guide the recording tape in contact therewith; and a torsion spring fitted
onto the shaft for the tape tension imparting member at its proximal end, one of two
free ends of the torsion spring being secured to the operative arm for the tape tension
imparting member with the other free end engaged with the pressure member or a part
near the pressure member, the torsion spring urging the tape tension imparting member
to cause it to pivot, thereby bringing the pressure member into contact with the recording
tape, the operative arm for the tape tension imparting member having a limiting opening
integral with or separate from the slot and serving to limit the range of pivotal
motion of the tape tension imparting member. When the operative arm for the tape tension
imparting member and the pinch roller and retracted into the stand-by position, the
projection is engaged with one side wall of the limiting opening to hold the tape
tension imparting member in a stand-by position where the pressure member is kept
away from the recording tape. When the operative arm for the tape tension imparting
member and the pinch roller are shifted to the position of the recording tape, the
pressure member is brought into contact with the pressure member so that the tape
tension imparting member is forced back by the tension of the recording tape to engage
the projection with the side wall of the limiting opening which is opposite to the
aforesaid one side wall.
[0011] Other objects and features of the present invention will become apparent from the
following explanation with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Fig. 1 is a plan view showing the essential portion of a video tape recorder (VTR)
as a first embodiment of the present invention, that is, a pinch roller and tension
imparting members;
Fig. 2 is a plan view showing a mechanism for driving reel supporting disks in the
VTR of Fig. 1;
Fig. 3 is a partially cross-sectional side elevational view showing the essential
portion of the reel-supporting-disk driving mechanism of Fig. 2;
Fig. 4 is a partially cross-sectional side elevational view showing the essential
portion of another part of the reel-supporting-disk driving mechanism of Fig. 2;
Fig. 5 is a plan view showing the primary inner mechanism of the VTR;
Fig. 6 is a plan view showing a mechanism for driving the pinch roller;
Fig. 7 is a plan view similar to Fig. 5, and serves to illustrate the state of the
inner mechanism during tape running;
Fig 8 is a plan view similar to Fig. 6, and serves to illustrate the state of the
inner mechanism during running of recording tape;
Fig. 9 is an essential enlarged view of Fig. 8; and
Fig. 10 is an essential enlarged view similar to Fig. 8, and servs to illustrate a
state wherein the recording tape is running in the opposite direction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] Fig. 5 shows the whole of the primary inner mechanism of a VTR according to a first
embodiment of the present invention when in a stop mode. Figs. 2 and 3 shows the essential
portion of that mechanism. As illustrated, a pair of reel shafts 2a and 3a is provided
on a chassis (or board) 1, and reel supporting disks 2 and 3 are rotatably fitted
onto the reel shafts 2a and 3a, respectively. A capstan (or capstan shaft) 5a is disposed
integrally with the rotor of a DD capstan motor 4, and a pulley 5 is fitted onto the
capstan 5a so that the pulley 5 can rotate integrally with the capstan 5a.
[0014] A shaft 6a is mounted on the chassis 1 in an upright posture, and a pulley gear 6
made up of a pulley 6b and a gear is rotatably fitted onto the shaft 6a. A belt 46
is passed around the pulley 6b and a pulley 5. A shaft 8a is a fixed shaft which is
located in the middle of the interval between the reel shafts 2a and 3a (a position
corresponding to approximately half the distance between these shafts), and a driving
gear 7 which is meshed with the pulley gear 6 is rotatably fitted onto the shaft 8a
(refer to Figs. 2 and 3). The driving gear 7 is a vertical two-stage gear which consists
of gears 7a and 7b. The driving gear 7 (or gear 7b) is meshed with a rotatable idler
gear 10 which is fitted onto a shaft 9a. The shaft 9a is secured to one end of an
idler arm 9 which is pivotally supported on a pivot shaft 8a. A fe!t spacer 11 is
interposed between the idler arm 9 and the idler gear 10. The felt spacer 11 is supported
on its back side by the gear 10 which is urged to push the spacer 11 by a spring (or
compression coiled spring) 12 supported on a spring seat 13 backed up by a stopper
14 secured to the end of the shaft 9a which is opposite to the idler arm 9. The spring
12 is held between the idler gear 10 and the spring seat 13 fitted onto the shaft
9a. The resilient force of the spring 12 strongly forces the felt spacer 11 against
the ideler arm 9 to produce the friction torque required to cause oscillation of the
arm 9 (as indicated by double-headed arrow A in Fig. 2). The idler arm 9 is movable
in the vertical opposite directions along the pivot shaft 8a as indicated by double-headed
arrow B (refer to Fig. 3). The vertical position of the idler arm 9 is determined
by a switching arm 15 which is arranged to retain bosses 9b (or engagement pins) which
is provided on the idler arm 9.
[0015] It is assumed here that the switching arm 15 is located at a lower position to hold
the idler arm 9 at a corresponding lower position. (Incidentally, in Fig. 3, the
swtiching arm 15 is shown as being located at an upper position. Fig. 4 is a cross-sectional
view showing the reel supporting disk 3 and a coupling mechanism associated therewith.
The idler gear 10 is meshed with a coupling gear 16, and the gear 16 and a gear 18
which is meshed with a gear portion 17 of the reel supporting disk 3 are arranged
to generate a predetermine torque by means of an existing friction coupling mechanism
made up of felt spacers 19a, 19b, a spring 20, a stopper 21 and a pressure member
22. The aforesaid gears 16 and 18 are supported for rotation about shafts 16a and
16b on the chassis 1, respectively.
[0016] Referring to Fig. 2, a switching arm 23 is pivotally supported by a pivot shaft 23a
on the chassis 1 and is pressed in position by the cooperation between a torsion spring
24 and a stop washer 25. The switching arm 23 retains an arm of the torsion spring
24 between a pair of projections 23b so that it is biased by the resulting spring
force in one direction as shown by a dot-dashed line. The end portion of the arm of
the torsion spring 24 extends into an opening formed in the switching arm 15. The
switching arm 15 is pivotally supported by a bearing 27, which is provided on the
chassis 1, so that it can rotate about an axis parallel to the upper surface of the
chassis 1.
[0017] The idler arm 9 moves up and down along the shaft 8a in accordance with the pivotal
motion of the switching arm 15 so that the idler gear 10 can selectively engage with
the coupling gear 16 and the gear 18. In this arrangement, if a strong torque is needed
for purposes of forward feed or rewinding, the idler arm 9 moves to its upper position
(the state shown in Figs. 2 and 3) to engage the idler gear 10 with the gear 18. Accordingly,
the rotational force is directly transmitted to the gear portion 17 of the reel supporting
disk 3 so that the rotational torque of the DD capstan motor 4 is transmitted to the
reel supporting disks 2 and 3 through the belt 46 with the coupling mechanism described
above bypassed. The switching arm 23 which is pivotally supported on the chassis 1
is rotated in the clockwise direction by a cam arm 26 which will be described later.
When the switching arm is rotated by a predetermined amount, the arm of the torsion
spring 24, which is retained between the projections 23b uprightly provided on the
switching arm 23, is biased in the clockwise direction as in Fig. 2 (as shown by a
solid line). The switching arm 15 is thereby urged in the counterclockwise direction
as viewed in the side elevational view of Fig. 3.
[0018] Referring to Fig. 5, an arm 44 is pivotally supported at a location below a fixed
guide 45 by a pivot shaft 45a (which is a pivot shaft serving to impart tape tension)
of the fixed guide (tape guide post) 45 which serves to define the running height
of recording tape 36. A pin 44a which serves as a pressure member is uprightly provided
on one end of the arm 44. The pin 44a is located so that it can come into contact
with the recording tape 36 positioned between the capstan shaft 5a and the fixed guide
45 and the pinch roller 42. By rotating the arm 44 about the pivot shaft 45a, the
pin 44a can be pressed against the recording tape 36 by a predetermined amount during
reproduction.
[0019] Referring to Fig. 1, a slider 46 serving as an arm for operating the tape tension
imparting member is pivotally fitted onto a shaft 42b which supports the pinch roller
42 for rotation about its axis. The slider 46 is arranged to be relatively displaced
in sliding contact with the outer periphery of the proximal end portion of the arm
44 which is fitted onto the pivot shaft 45a. A slot 46b and a limiting opening 46a
which extends from it are formed in the slider 46, and a projection 44b of the arm
44 is engaged with this opening. A torsion spring 47 is looped around the pivot shaft
45a to urge the arm 44 in the counterclockwise direction.
[0020] Then, an arrangement associated with the driving system is briefly explained. Referring
to Fig. 6, as a reversible loading motor 33 runs in one direction, a cam gear 34 is
caused to rotate by means of a predetermined speed reducing mechanism in the counterclockwise
direction. Simultaneously, a known speed reduction driving mechanism which is not
shown is activated to drive the tape guide members 35a and 35b shown in Fig. 5, thereby
drawing the recording tape 36 out of a tape cassette (not shown). Then, the tape guide
members 35a and 35b are, as shown in Fig. 7, moved into contact with corresponding
stoppers 37a and 37b to wind the recording tape 36 around a rotary head cylinder 39.
At this time, the recording tape 36 is also brought into contact with a sound controlling
head 38 (refer to Figs. 5, 7 and 10). In this manner, a predetermined tape running
path is formed as shown in Fig. 7.
[0021] Referring back to Fig. 6, the cam gear 34 is rotatably supported by a shaft 34b on
the chassis 1, and a cam groove 34a is formed in one side of the cam gear 34. The
cam arm 26 having an uprightly extending pin 26b is pivotally fitted onto a shaft
26a on the chassis 1, and the pin 26b is engaged with the cam groove 34a. As the cam
gear 34 rotates, the cam arm 26 is caused to rotate in accordance with a predetermined
cam lift. The other end of the cam arm 26 is engaged with a link mechanism 40 which
is pivotally supported by a shaft 40a on the chassis 1, thereby constituting an existing
toggle mechanism. When the pinch roller 42 is pressed against the capstan 5a, the
cam arm 26 acts to urge a first pinch roller arm 41a as shown in Fig. 8. Although
no detailed explanation is given, the first pinch roller arm 41a is supported pivotally
about the shaft 42a on the chassis 1 and is combined with a second pinch roller arm
41b in pairs. A torsion spring 43 is set between the first pinch roller arm 41a and
the second pinch roller arm 41b so as to create a predetermined force which acts to
press the pinch roller 42.
[0022] As described previously in connection with Fig. 1, the slider 46, which is supported
pivotally about the shaft 42b of the pinch roller 42, is arranged to be relatively
displaced in sliding contact with the outer periphery of the proximal end portion
of the arm 44 which is fitted onto the pivot shaft 45a. Accordingly, as the pinch
roller arm 41b rotates, the slider 46 is displaced relative to the proximal end portion
of the arm 44. During this time, the limiting opening 46a of the slider 46 having
a cam-like configuration is engaged with the projection 44b of the arm 44 which is
urged for rotation, and limits the projection 44b in position, thereby determining
the attitude of the entire arm 44. More specifically, when the tape guide members
35a and 35b are located at a casette loading position, the arm 44 is sufficiently
set aside from the position of the recording tape 36 so as not to hinder loading or
unloading of a tape cassette. As shown in Figs. 7 and 9, when the pinch roller 42
is pressed against the capstan 5a, that is, in a pause mode during recording or playback,
the projection 44b of the arm 44 is released from its limited state to allow the pin
44a to press the recording tape 36 by the rotational urging force of the torsion spring
47. During a recording or playback mode, however, the tape tension created at this
part is normally on the order of 60-100 gram. Accordingly, by setting the rotational
urging force to a pressure of 10 gram or less, the arm 44 is rotated in the counterclockwise
direction to bring the projection 44b into contact with one side wall of the slider
46 which faces the limiting opening 46a, thereby determining the position of the pin
44a as illustrated.
[0023] The following is an explanation of the operation of the aforesaid mechanism during
a pause mode. Although no detailed explanation is given, if an operator presses a
"pause" switch (not shown), the driving of the recording tape 36 is stopped, that
is, the capstan motor 4 of Fig. 2 stops. At this time, the belt 46, which is passed
around the pulley 5 of the capstan motor 4 and the pulley gear 6 of a tape rewinding
mechanism, acts to cancel the difference in tension between an extended portion and
a contracted portion, thereby causing reversal of the capstan motor 4, namely, a so-called
backlash. Accordingly, in Fig. 10, the recording tape 36 is also reversed by a slight
amount to reduce the tape tension. At this time, however, the pin 44a, which is uprightly
provided on the arm 44, acts to presses the recording tape 36 by an amount corresponding
to a decrease in the tape tension, and the arm 44 is displaced in the clockwise direction.
The pin 44a on the arm 44 suffices to press the portion of the recording tape 36 which
is very near to a loosened portion to such an extent that the looseness is adequately
absorbed. It is therefore possible to set the pressure of the pin 44a to a sufficiently
small level. In this maner, since the recording tape 36 is pressed in accordance with
the tape tension, it is possible to obtain the required tension without the use of
any drive source. In many cases, a decrease in tape tension at a tape entrance side
around the rotary head cylinder 39 becomes problem in terms of performance. However,
even if the aforesaid pressure is set to the sufficiently small level, a decrease
in tape tension at the tape entrance side around the rotary head cylinder 39 can be
minimized owing to contract loads produced between the recording tape 36 and the tape
guide post 45, the sound controlling head 38, the tape guide member 35b and other
elements. Accordingly, the deterioration of the performance is lessened.
[0024] As is apparent from the foregoing, a magnetic recording/playback apparatus according
to the present invention have been proposed. With this apparatus, even if a backlash
occurs in the motion of a capstan motor immediately after a pause, it is possible
to prevent an excessive decrease in tape tension and the deterioration of performance.
1. A magnetic recording/playback apparatus of the type which utilizes to take-up reel
driving mechanism arranged to transmit power from a pulley to a rewinding mechanismm
through a belt, said pulley being provided on a direct drive capstan motor, and which
is arranged to draw a recording tape into a predetermined path for purposes of recording
or playback, comprising:
a rotary head cylinder arranged to record signals on said recording tape to play back
signals recorded on said recording tape;
a pinch roller cooperative with a capstan shaft to clamp and drive said recording
tape; and
a tension imparting member capable of coming into and out of contact with said recording
tape and arranged to press said recording tape by a predetermined pressure by means
of the urging force of an urging spring while signals are being recorded on said recording
tape, while signals recorded on said recording tape are being played back, and in
a pause.
2. A magnetic recording/playback apparatus according to claim 1, wherein said tape
tension imparting member is disposed at a location corresponding to the tape running
section between the position of a sound controlling head and the position at which
said recording tape is clamped between said capstan shaft and said pinch roller.
3. A magnetic recording/playback apparatus according to claim 1, wherein said tape
tension imparting member is a member which serves to displace said recording tape
from an ordinary running path during a pause to thereby absorb the looseness of said
recording tape and impart a predetermined tension to said recording tape.
4. A magnetic recording/playback apparatus according to claim 1, wherein said tape
tension imparting member urged by an urging spring is a pivotal member which pivots
on a shaft, said tape tension imparting member bearing at one end a pressure member
which smoothly guides said recording tape in contact therewith.
5. A magnetic recording/playback apparatus according to claim 4, wherein the pressure
member of said tape tension imparting member is kept away from said recording tape
except when signals are recorded on said recording tape, except when signals recorded
on said tape are played back and except during a pause.
6. A magnetic recording/playback apparatus according to claim 4, wherein a shaft for
said tape tension imparting member is secured to a board.
7. A magnetic recording/playback apparatus of the type which utilizes a take-up reel
driving mechanism arranged to transmit power from a pulley to a rewinding mechanism
through a belt, said pulley being provided on a direct drive capstan motor, and which
is arranged to draw a recording tape into a predetermined path for purposes of recording
or playback, comprising:
a rotary head cylinder arranged to record signals on said recording tape and to play
back signals recorded on said recording tape;
a pinch roller cooperative with a capstan shaft to clamp and drive said recording
tape;
a pivotal arm for said pinch roller arranged to reciprocally pivot in accordance with
the motion of a cam member driven by a motor;
a pinch roller shaft secured to one end of said pivotal arm for supporting said pinch
roller;
an operative arm for said tape tension imparting member pivotally supported at one
end by said pinch roller shaft and provided with a slot at the other end, said shaft
for said tape tension imparting member extending through said slot, said operative
arm being restricted by said shaft for said tape tension imparting member at said
other end but permitting the pivotal motion of said pivotal arm for said pinch roller
within a predetermined range in that said shaft for said tape tension imparting member
can be relatively displaced in said slot;
a tape tension imparting member pivotally supported at one end on said shaft for said
tape tension imparting member and provided with a pressure member at the other end
and a projection at or near said other end, said pressure member extending along the
axis of said shaft for said tape tension imparting member and serving to smoothly
guide said recording tape in contact therewith; and
a torsion spring fitted onto said shaft for said tape tension imparting member at
its proximal end, one of two free ends of said torsion spring being secured to said
operative arm for said tape tension imparting member with said other free end engaged
with said pressure member or a part near said pressure member, said torsion spring
urging said tape tension imparting member to cause it to pivot, thereby bringing said
pressure member into contact with said recording tape;
said operative arm for said tape tension imparting member having a limiting opening
integral with or separate from said slot and serving to limit the range of pivotal
motion of said tape tension imparting member;
when said operative arm for said tape tension imparting member and said pinch roller
are retracted into the stand-by position, said projection being engaged with one side
wall of said limiting opening to hold said tape tension imparting member in a stand-by
position where said pressure member is kept away from said recording tape; and
when said operative arm for said tape tension imparting member and said pinch roller
are shifted to the position of said recording tape, said pressure member being brought
into contact with said pressure member so that said tape tension imparting member
is forced back by the tension of said recording tape to engage said projection with
the side wall of said limiting opening which is opposite to said one side wall.
8. A magnetic recording/playback apparatus according to claim 7, wherein a tape guide
post is secured to said shaft for said tape tension imparting member.